My friends have a smallish car (Astra) and have a Graco 2 part system car seat...you know, the ones with the base unit and then the capsule that clicks in. It works really well with their car and is a really good seat. Here, they cost about $320 or so when you convert currency but I'm not sure what thy cost in Oz if they are sold there.

We're being given my friends Graco 2 part capsule but I never thought about the fit as we have a reasonably large car...guess I should check!